Image sensor and readout method

ABSTRACT

The invention relates to an image sensor, in particular a CMOS image sensor, for electronic cameras, having a plurality of light sensitive pixels arranged in rows and columns and a number of output amplifiers. The image sensor is made such that the order in which the pixels are switched to the output amplifiers is varied with respect to the order in which the pixels are arranged along a row of the image sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of German Patent Application No. 102007 027 463.9 filed Jun. 14, 2007.

FIELD OF THE INVENTION

The present invention relates to an image sensor, in particular to aCMOS image sensor, for electronic cameras, having a plurality of lightsensitive pixels arranged in rows and columns, furthermore having anumber of output amplifiers, furthermore having a switching device forselectively switching the pixels of one of the rows to the outputamplifiers and having a control device for controlling the switchingdevice.

BACKGROUND OF THE INVENTION

Known electronic cameras include an image sensor which comprises aplurality of light sensitive elements or pixels which are arranged inrows and columns and which convert light incident through a lens of thecamera into electrical signals. For the reading out of an image, each ofthe pixels is addressed and a signal which is proportional to a chargeof the pixel collected by an exposure is directed to an output of theimage sensor.

In cameras which simultaneously have a high number of light sensitiveelements and a high frame rate, image sensors are used which have aplurality of outputs which can be read out in parallel—and thusfaster—in a respective readout cycle. In addition, the columns can bedivided into column groups which each have a plurality of columns, withthe number of the columns in each of the column groups corresponding tothe number of the outputs.

In this connection, the rows are associated with the outputs of theimage sensor in the manner of unit matrices disposed next to one anotherso that the columns with the numbers n, n+a, n+2a, etc. are eachassociated with the output with the number n, with the columns and theoutputs each being numbered continuously.

With an image sensor with 32 outputs and with a division of the columnsinto column groups, for example, in a first readout cycle, the 1stcolumn of the image sensor which corresponds to the 1st column of the1st column group is thus associated with the 1st output. The 2nd columnof the image sensor which corresponds to the 2nd column of the 1stcolumn group is associated with the 2nd output, etc. up to the 32ndcolumn of the image sensor which corresponds to the 32nd column of the1st column group which is associated with the 32nd output. In thefollowing readout cycle, the 33rd column of the image sensor whichcorresponds to the 1st column of the 2n column group is again associatedwith the 1st output; the 34th column of the image sensor whichcorresponds to the 2nd column of the 2nd column group is againassociated with the 2nd output, etc.

Each of the outputs of the image sensor has its own output amplifier,with the signals of the pixels being amplified by the output amplifierin order subsequently to be digitized. The signals are applied to theoutput amplifiers as analog electrical voltages which correspond to thecollected charges.

The reading out of such an image sensor usually takes place row-wise,i.e. row for row. Within the respectively selected line, the signals ofthe associated pixels are switched to the outputs of the image sensorvia corresponding control signals column-wise, i.e. column for column,or optionally column-group-wise, i.e. column group for column group,with the readout starting at a 1st column or column group located at anedge of the image sensor and being continued in increasing order withthe respective directly adjacent column or column group, i.e. accordingto the arrangement order of the columns or column groups. It followsfrom this that the signals of the pixels of the 1st, 33rd, 65th, etc.column of the image sensor are output sequentially at the 1st output orat the 1st output amplifier respectively, that the signals of the pixelsof the 2nd, 34th, 66th, etc. column of the image sensor are output atthe 2nd output or 2nd output amplifier respectively, etc.

A strictly regular order is thus provided with known image sensors inwhich the signals of the pixels are switched to the output amplifier.

It is known that the respective signal currently applied at an outputamplifier always includes a small portion, disposed in the perthousandth range, of the signal directly amplified beforehand by therespective output amplifier, said portion being caused, for example, bythermal effects and/or feedback effects on the power supply. Suitablecircuits and calculation methods are known to counter the disturbinginfluence of the signal of the predecessor pixel. A completecompensation is, however, not possible.

If the image sensor only has one single output, and thus only one outputamplifier, the signals of all the pixels are amplified by the sameoutput amplifier, with the signals of pixels arranged directly next toone another being amplified directly sequentially such that the portionof the signal of the respective predecessor pixel is effective in thesignal of the pixel arranged directly adjacent to the respectivepredecessor pixel. This admittedly generates a kind of blur in the imagewith large difference between two signals amplified directly after oneanother. However, this is not perceivable by the eye.

If the image sensor, however, has a plurality of outputs, as has beenexplained by way of example above, the portion of the signal of therespective predecessor pixel—that is the portion of the signal amplifieddirectly beforehand—makes itself noticeable in the amplification of thesignal of that pixel which is arranged remote from the predecessor pixelby the number of outputs. The signals of the pixels arranged between thepredecessor pixel and the pixel remote from the predecessor pixel by thenumber of outputs are namely amplified by the output amplifiers of theother outputs. For example, in an image which shows a bright candleflame in an otherwise dark room, a visual echo of the candle flame isgenerated which is laterally offset from the original candle flame. Suchan image interference is called a ghost image. In the example chosen,the ghost image is particularly easily visible since the echo occurs ina dark region. For example, with an image sensor having 32 outputs, theecho is offset from the original by 32 pixels.

SUMMARY OF THE INVENTION

It is the underlying object of the invention to provide an image sensorof the initially named kind which enables the occurring of ghost imagesto be suppressed.

This object is satisfied by an image sensor having the features of claim1, and in particular in that the order in which the pixels are switchedto the output amplifiers is varied with respect to the order in whichthe pixels are arranged along a row of the image sensor.

With the image sensor in accordance with the invention, the signals ofthe pixels of a row can also be read out column-group-wise, i.e. thesignals of the pixels of a column group of the respective row can beread out together in a respective readout cycle or the signals of thepixels of a row are read out column-wise.

The signals of the pixels are switched to the individual outputamplifiers by a corresponding control of the switching device inaccordance with such a spatial or temporal order from column to columnor optionally within a respective column group (i.e. within a readoutcycle) or optionally from column group to column group (i.e. fromreadout cycle to readout cycle), said order being different with respectto the order in which the pixels are arranged along the respective rowof the image sensor.

It is hereby ultimately achieved that the spatial spacing of the pixelswhose signals are switched sequentially to a specific one of theplurality of output amplifiers is varied. This change in the switchingorder or of the pixel spacing takes place at least for a plurality ofoutput amplifiers, preferably for all the output amplifiers. Theinitially explained ghost images are hereby scrambled into one anotherso that they are no longer perceivable by the eye.

In accordance with an advantageous embodiment, the columns are dividedinto a plurality of column groups and the number of output amplifierscorresponds to the number of columns of a column group, with the columnsof each column group being associated with the output amplifiers inaccordance with an association order and with a plurality of mutuallydifferent association orders being provided for the plurality of columngroups. In other words, the orders in which the columns (and thus thepixels) of a respective column group are associated with the outputamplifiers differ for the plurality of column groups. The association ofthe individual columns of a respective column group with the outputamplifiers of the image sensor thus does not take place, or does nottake place exclusively, in accordance with the manner of a unit matrixexplained above.

A respective association order is preset, for example, by thedistribution of association points at which a column of the image sensoris linked or linkable to a respective horizontal output line of a signalbus, said output line in turn being switchable to a specific one of theplurality of output amplifiers of the image sensor. These associationpoints are either fixedly preset (by a permanent electrical connectionbetween the respective column line and the respective output line). Orselectively variable association points are provided, with a respectiveswitch being arranged at the respective association points.

At least some of the column groups preferably have mutually differentassociation orders. The association order of the columns of a columngroup with the output amplifiers is therefore different from theassociation order of the columns of another column group with the outputamplifiers. The association orders of all column groups can inparticular be different from one another.

It is in particular possible that different association orders areprovided for respective adjacent column groups. For example, theodd-number column groups of the image sensor can have a firstassociation order and the even-number column groups can have a secondassociation order, with the first and second association orders beingdifferent from one another. A sufficient scrambling of ghost images canhereby be achieved in cases in which the arrangement order of the columngroups corresponds to the readout order of the column groups.

In accordance with an embodiment of the invention, a plurality of signalbuses are provided which each include a number of output lines whichcorresponds to the number of output amplifiers, with the signal buses inparticular being able to be selectively switched to the outputamplifiers by means of a switching device made as a multiplexer device.High settling times can hereby be accepted with small signal bandwidthsin order nevertheless to achieve high readout rates. The output lines ofthe signal buses are provided for the purpose of connecting the outputamplifiers to the columns of the column groups. For example, the controldevice can be made to control the switching device such that two columngroups sequentially switched to the output amplifiers are switched tothe output amplifiers via different ones of the signal buses.

Some or all of the column groups are in particular associated with aplurality of or all of the signal buses, with the association ordersbeing different for the respective signal buses within each such columngroup. It is in particular hereby made possible for the associationorder to be varied from row to two within a column group. For thispurpose, the columns of the respective column group can be switched todifferent signal buses from row to row. A further scrambling can herebybe achieved.

A further scrambling can be achieved if the control device is made tocontrol the switching device such that the signal buses are switched tothe output amplifiers from row to row in different orders.

In accordance with a further development, the image sensor can be readout completely using a readout sequence, with the image sensor, however,having more signal buses than are actually required for the reading outof a regular readout sequence. A signal bus redundant with respect to acomplete readout is consequently provided. If, for example, the imagesensor has 5 signal buses, but only 4 signal buses are required for thereading out, a bus association order can thus be used, if one of thesignal buses is defective, in which the defective signal bus is notused.

In accordance with a further embodiment, and indeed alternatively oradditionally to the different spatial association orders, the imagesensor is controlled such that the chronological readout order,according to which the column groups are sequentially connected to theoutput amplifiers, is different from the arrangement order, according towhich the column group are arranged next to one another in the directionof a row, with the columns being divided into a plurality of columngroups and the number of output amplifiers corresponding to the numberof columns of a column group. In other words, the different columngroups are not switched to the output amplifiers in the same order inwhich the column groups are arranged next to one another.

A ghost image whose original extends over a plurality of column groupsis, for example, hereby also divided along the borders of the columngroups, with the individual parts of the ghost image being able toappear scrambled at different positions within the image such that theghost image can no longer be perceived by the eye. It is particularlyeffective for the variation of the chronological order of the readingout of the column groups to be combined with the explained variation ofthe spatial association order of the columns to the output amplifiers.

If there is no division into column groups, the columns can also bearranged in accordance with an arrangement order relative to one anotherand the control device can be made to control the switching device suchthat the columns are switched for each row in accordance with arespective readout order sequentially to the output amplifiers, with thereadout order of the columns being different from the arrangement orderof the columns.

This scrambling can furthermore be improved in the two aforesaid casesin that the readout order is also varied from row to row.

In accordance with a further embodiment, the image sensor has at leastone signal bus, each of which includes a number of output lines whichcorresponds to the number of output amplifiers, with the columns beingable to be connected to a plurality of or all of the output lines of theat least one signal bus at preset association points. This enables anydesired association of the columns with the output amplifiers. Adefective output can hereby also be bypassed.

The invention also relates to a corresponding method for the reading outof an image sensor, in particular of an CMOS image sensor, forelectronic cameras.

A non-restrictive embodiment of the invention, which illustrates acombination of a plurality of measures for the scrambling of a ghostimage, is shown in the drawing and will be described in the following.

BRIEF DESCRIPTION OF THE DRAWINGS

There are shown, schematically in each case:

FIG. 1 a first embodiment of an image sensor in accordance with theinvention;

FIG. 2 a second embodiment of an image sensor in accordance with theinvention;

FIG. 3 a part of a third embodiment of an image sensor in accordancewith the invention; and

FIG. 4 a part of a fourth embodiment of an image sensor in accordancewith the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The image sensor shown in FIG. 1 has a plurality of light sensitivepixels P which are arranged in rows (shown horizontally here) andcolumns (shown vertically here). For reasons of clarity, only of thepixels P is provided with a reference symbol. Each row has a rowselection line . . . , Z_(m-1), Z_(m) for the pixels P associated withthe respective row and each columns comprises a column line S₁₋₁, . . ., S₁₋₄, S₂₋₁, . . . , S₂₋₄, . . . for the pixels P associated with therespective column. The column lines S₁₋₁, . . . , S₁₋₄, S₂₋₁, . . . ,S₂₋₄, . . . are divided into column groups S₁, S₂, . . . which eachinclude four column lines S₁₋₁, . . . , S₁₋₄, S₂₋₁, . . . , S₂₋₄, . . ..

The image sensor furthermore includes a row selection circuit 11 bywhich a respective one of the rows . . . , Z_(m-1), Z_(m) can beselected for the reading out of the signals of the pixels P of this line. . . , Z_(m-1), Z_(m). A column selection circuit 13 is furthermoreprovided by which a respective one of the plurality of column groups S₁,S₂, . . . can be selected for the reading out of the signals of thepixels P of this column group S₁, S₂, . . . . For this purpose, aseparate column selection switch 19 (of which only one is provided witha reference numeral) is provided for each of the column lines S₁₋₁, . .. , S₁₋₄, S₂₋₁, . . . , S₂₋₄, . . . , with the column selection switch19 of each column group S₁, S₂, . . . being controllable via a commoncolumn selection line 21 by the column selection circuit 13 so that thecolumn selection switches 19 of each column group S₁, S₂, . . . are eachswitchable together. A separate column amplifier 23 is connected beforeeach of the column selection switches 19. The line selection circuit 11,the column selection circuit 13, the column selection switches 19, thecolumn selection control lines 21 as well as optionally a bus selectioncircuit, a bus selection switch and a bus selection control line, whichwill be explained in more detail in the following, form part of aswitching device of the image sensor which is controlled by a controldevice, for example by a microcontroller 17.

The image sensor furthermore has a signal bus which in the example shownhere includes four output lines A₁, A₂, A₃, A₄ to which the signals ofthe pixels of a row . . . , Z_(m-1), Z_(m) of a column group S₁, S₂, . .. can be switched, with each of the output lines A₁, A₂, A₃, A₄ beingconnected to their own output amplifier V₁, V₂, V₃, V₄.

In this connection, each column line S₁₋₁, . . . , S₁₋₄, S₂₋₁, . . . ,S₂₋₄, . . . of each column group S₁, S₂, . . . is unambiguouslyassociated with a respective output line A₁, A₂, A₃, A₄ and thus with arespective output amplifier V₁, V₂, V₃, V₄ in accordance with anassociation order, with the column groups S₁, S₂, . . . having mutuallydifferent association orders. The associations here are fixed electricalconnections between the column lines S₁₋₁, . . . , S₁₋₄, S₂₋₁, . . . ,S₂₋₄, . . . and the output lines A₁, A₂, A₃, A₄.

The following association orders are, for example present with the imagesensor shown in FIG. 1: The 1st column line S₁₋₁, of the 1st columngroup S₁ is associated with the 1st output line A₁, the 2nd column lineS₁₋₂ of the 1st column group S₁ is associated with the 3rd output lineA₃, the 3rd column line S₁₋₃ of the 1st column group S₁ is associatedwith the 2nd output line A₂, and the 4th column line S₁₋₄ of the 1stcolumn group S₁ is associated with the 4th output line A₄, as can berecognized with reference to association points Z. Furthermore, the 1stcolumn line S₂₋₁ of the 2nd column group S₂ is associated with the 3rdoutput line A₃, the 2nd column line S₂₋₂ of the 2nd column group S₂ isassociated with the 4th output line A₄, the 3rd column line S₂₋₃ of the2nd column group S₂ is associated with the 2nd output line A₂, and the4th column line S₂₋₄ of the 2nd column group S₂ is associated with the1st output line A₁. Furthermore, the 1st column line S₃₋₁ of the 3rdcolumn group S₃ is associated with the 3rd output line A₃, the 2ndcolumn line S₃₋₂ of the 3rd column group S₃ is associated with the 2ndoutput line A₂, the 3rd column line S₃₋₃ of the 3rd column group S₃ isassociated with the 4th output line A₄, and the 4th column line S₃₋₄ ofthe 3rd column group S₃ is associated with the 1st output line A₁.

The reading out of the image sensor in accordance with the inventionshown in FIG. 1 will be described in the following.

The reading out takes place row-wise by application of correspondingaddress signals to the row selection circuit 11, with the row selectionlines . . . , Z_(m-1), Z_(m) being addressed sequentially in risingorder starting at a first row selection line located at an edge of theimage sensor. Per row, the reading out takes place column group-wise,i.e. the pixels P associated with the respective selected row are readout column group for column group by a corresponding control of thecolumn selection switches 19 by the column selection circuit 13. Sincethe association orders of the column groups S₁, S₂, . . . to the signalbus are different from one another, a scrambling of a ghost image can beachieved.

To further increase the scrambling, the control device 17 of the imagesensor can be made to control the column selection switches 19 by thecolumn selection circuit 13 such that the readout order of the columngroups S₁, S₂, . . . is varied from row to row. For this purpose, theimage sensor is configured such that the readout order of the columngroups for at least some of the rows . . . , Z_(m-1), Z_(m) does notcoincide with the arrangement order of the column groups S₁, S₂, . . . .The column groups S₁, S₂, . . . are therefore not read out in risingorder, that is not first the 1st column group S₁, then the 2nd columngroup S₂, then the 3rd column group S₃, etc. The column groups S₁, S₂, .. . are rather read out more or less randomly, i.e., for example, firstthe 37th column group S₃₇, then the 7th column group S₇, then the 22ndcolumn group, etc.

In a variant of the embodiment in accordance with FIG. 1, deviating fromthe representation in accordance with FIG. 1, always the sameassociation order is provided, for example in the known manner of a unitmatrix, for the different column groups S₇₁, S₂, . . . . A scrambling ofa ghost image is in this case exclusively achieved in that the readoutorder of the column groups S₁, S₂, . . . is varied for at least some ofthe rows, as described in the preceding paragraph.

With the image sensor shown in FIG. 2, unlike the image sensor shown inFIG. 1 which only has one signal bus, two signal buses B₁, B₂ areprovided which each have four output lines A₁, A₂, A₃, A₄, with the oddnumber column groups S₁, S₃, . . . being associated with the firstsignal bus B₁ and the even number column groups S₂, S₄, . . . beingassociated with the second signal bus B₂. Generally, however, any otherassociation of the column groups S₁, S₂, S₃, . . . with the signal busesB₁, B₂ is possible. The association orders of the individual columngroups S₁, S₂, S₃, . . . correspond in another respect to theassociation orders shown in FIG. 1 such that the column groups S₁, S₂, .. . shown in FIG. 2 also have mutually different association orders.

Furthermore, a bus selection circuit 15 is provided which iscontrollable by the microcontroller 17 and which makes it possible viatwo bus selection control lines 27 to switch one of the two signal busesB₁, B₂ selectively to the output amplifiers V₁, V₂, V₃ V₄, with the 1stoutput line A₁ of the respective signal bus B₁, B₂ being switchable tothe 1st output amplifier V₁, the 2nd output line A₂ of the respectivesignal bus B₁, B₂ to the 2nd output amplifier, the 3rd output line A₃ ofthe respective signal bus B₁, B₂ to the 3rd output amplifier, and the4th output line A₄ of the respective signal bus B₁, B₂ to the 4th outputamplifier. For this purpose, a separate bus selection switch 25 (ofwhich only two are provided with a reference numeral) are provided foreach of the output lines A₁, A₂, A₃, A₄, with the bus selection switches25 of each signal bus B₁, B₂ being controllable via a respective commonbus selection control line 27 by the bus selection circuit 15 so thatthe bus selection switches 25 of each bus B₁, B₂ can each be switchedtogether.

An increase in the readout speed can be achieved by the provision of aplurality of buses B₁, B₂. While the signals of the pixels P of aselected column group S₁, S₂, . . . of a selected row . . . , Z_(m-1),Z_(m) are switched via the one signal bus B₁ or B₂ to the outputamplifiers A₁, A₂, A₃, A₄, the pixels P to be read out next can namelyalready be selected by means of the row selection circuit 11 and thecolumn selection circuit 13. A settling of these signals on therespective other signal bus B₂ or B₁ is hereby enabled at an early time,namely before the application of the signals of the pixels P to be readout next at the output amplifiers A₁, A₂, A₃, A₄. Reading out can thusalso take place at a high cycle frequency with longer settling times.

Analog to the control device of the image sensor in accordance with FIG.1, the control device 17 of the image sensor in accordance with FIG. 2can optionally also be made to control the column selection switches 19by the column selection circuit 13 such that the readout order of thecolumn groups S₁, S₂, . . . can be varied from row to row.

The image sensor in accordance with FIG. 3 has three signal buses B₁,B₂, B₃ and is only shown in the region of the association of the columngroup S₁ with the signal buses B₁, B₂, B₃, with the column group S₁ onlybeing selected by way of example. The column group S₁, and equally theother column groups S₂, S₃, . . . , not shown, is associated with eachof the three signal buses B₁, B₂, B₃, with the association orders withineach column group S₁, S₂, . . . being different.

Furthermore, first column selection switches 19 a associated with theassociation points Z are provided for the 1st signal bus B₁, secondcolumn selection switches 19 b for the 2nd signal bus B₂ and thirdcolumn selection switches 19 c for the 3rd signal bus B₃ (of which onlyone respective column selection switch 19 a, 19 b, 19 c is provided witha reference numeral). These column selection switches 19 a, 19 b, 19 cmake it possible to switch the column groups S₁, S₂, . . . selectivelyin each case to a single one of the signal buses B₁, B₂, B₃, with thefirst column selection switches 19 a being controllable via a commoncolumn selection control line 21 a, the second column selection switchesbeing controllable via a common column selection control line 21 b, andthe third column selection switches being controllable via a commoncolumn selection control line 21 c by the column selection circuit notshown in FIG. 3 such that the column selection switches 19 a, 19 b or 19c can each be switched together.

In order, for example, to switch the 1st column group S₁ to the 1stsignal bus B₁, the first column selection switches 19 a are closed andthe second and third column selection switches 19 b, 19 c are opened. Inorder to switch the 1st column group S₁ to the 2nd signal bus B₂, thesecond column selection switches 19 a are closed and the first and thirdcolumn selection switches 19 a, 19 c are opened. In order to switch the1st column group S₁ to the 3rd signal bus B₃, the third column selectionswitches 19 c are closed and the first and second column selectionswitches 19 a, 19 b are opened.

Consequently, in contrast to the associations in the image sensors shownin FIGS. 1 and 2, the column lines S₁₋₁, . . . , S₁₋₄, S₂₋₁, . . . ,S₂₋₄, . . . are not fixedly associated with the output lines A₁, A₂, A₃,A₄. A number of different association orders which corresponds to thenumber of signal buses can rather be provided for each column group S₁,S₂, . . . . A further scrambling is hereby possible since a plurality ofdifferent association orders can be realized within a single columngroup from which a respective one can be selected.

In another respect, the design of the image sensor in accordance withFIG. 3 corresponds to the design of the image sensor in accordance withFIG. 2, with bus selection switches, however, also being provided,analog to the first two signal buses B₁, B₂, for the third signal bus B₃in the image sensor in accordance with FIG. 3, said bus selectionswitches being controllable via a common bus selection control line bythe bus selection circuit which is not shown in FIG. 3 so that one ofthe three signal buses B₁, B₂, B₃ can selectively be switched to theoutput amplifiers not shown in FIG. 3.

The image sensor in accordance with FIG. 3 is designed for a readoutsequence which only requires two signal buses, for example the twosignal buses B₁ and B₂, for a complete reading out. The 3rd signal busB₃ is a redundant signal bus which can be used as a replacement for oneof the two signal buses B₁, B₂ if one of the two signal buses B₁, B₂ isdefective.

The signal buses are preferably always switched to the output amplifiersin the same sequence on the reading out per row, i.e. the sequence isrepeated cyclically within the row, with the sequence being varied fromrow to row. A further scrambling can hereby be achieved and theamplified signals can easily be associated with the respective pixels Pto be able to correctly compensate the amplified signals to form a takenimage. For example, with an image sensor having four signal buses B₁,B₂, B₃, B₄ (not shown) and, optionally, a redundant signal bus B₅ (notshown), the signal buses for the reading out of the column groups S₁,S₂, . . . of the first row Z₁ can be switched in sequential readoutcycles in the order B₁, B₃, F₄, B₂, . . . to the output amplifiers V₁,V₂, V₃, V₄, for the reading out of the column groups S₁, S₂, . . . ofthe second row Z₂ in the order B₁, B₄, B₂, B₃, . . . , etc. Preset moreor less random orders can be used in this respect.

The image sensor in accordance with FIG. 4 is, unlike the image sensorsin accordance with FIGS. 1 to 3, not divided into column groups andincludes, in addition to a plurality of column lines SP₁, SP₂, . . . , asingle signal bus having four output lines A₁, A₂, A₃, A₄. The imagesensor in accordance with FIG. 4 is only shown in the region of theassociations of the first two column lines SP₁ and SP₂ with the outputlines A₁, A₂, A₃, A₄, with the two column lines SP₁ and SP₂ only beingshown by way of example. The column lines P₁ und SP₂, just like theother, not shown, column lines SP₃, SP₄, . . . , are associated witheach of the four output lines A₁, A₂, A₃, A₄.

For this purpose, there are provided, in each case associated with thecolumn lines SP₁, SP₂, . . . , first column selection switches 19 a forthe 1st output line A₁, second column selection switches 19 b for the2nd output line A₂, third column selection switches 19 c for the 3rdoutput line A₃, and fourth column selection switches 19 d for the 4thoutput line A₄. These column selection switches 19 a, 19 b, 19 c, 19 dmake it possible in the column selection circuit not shown in FIG. 4 toswitch the column lines SP₁, SP₂, . . . via respective column selectioncontrol lines 21 a, 21 b, 21 c, 21 d in each case selectively to asingle one of the output lines A₁, A₂, A₃, A₄.

In order, for example, to switch the 1st column line SP₁ to the 1stoutput line A₁, the first column selection switch 19 a is closed and thesecond, the third and the fourth column selection switches 19 a, 19 c,19 d are opened again. In order to switch the 1st column line SP₁ to the2nd output line A₂, the second column selection switch 19 b is closedand the first, the third and the fourth column selection switches 19 a,19 c, 19 d are opened again. In order to switch the 1st column line SP₁to the 3rd output line A₃, the third column selection switch 19 c isclosed and the first, the second and the fourth column selectionswitches 19 a, 19 b, 19 d are opened again. In order to switch the 1stcolumn line SP₁ to the 4th output line A₄, the fourth column selectionswitch 19 d is closed and the first, the second and the third columnselection switches 19 a, 19 b, 19 c are opened.

Analog to the associations in the image sensor shown in FIG. 3, in theimage sensor in accordance with FIG. 4, the column lines SP₁, SP₂, . . .are not fixedly associated with the output lines A₁, A₂, A₃, A₄. Eachcolumn line SP₁, SP₂, . . . can rather be associated with each of theoutput lines A₁, A₂, A₃, A₄. A scrambling can hereby be achieved in asimple manner, for example in that the columns along a respective roware switched to the amplifiers in a more or less random order.Alternatively or additionally, the readout order in which the columnlines SP₁, SP₂, . . . are sequentially switched to the output amplifierscan be varied with respect to the arrangement order of the columns alongthe row.

In addition, based on the arrangement shown in FIG. 4, a defectiveoutput can be bypassed in that the corresponding output line A₁ is nolonger used.

In another respect, the design of the image sensor in accordance withFIG. 4 corresponds to the design of the image sensor in accordance withFIG. 1, with the column lines SP₁, SP₂, . . . , however, contrary toFIG. 1, not being divided into column groups.

It is generally also possible to modify the image sensor in accordancewith FIG. 4 such that a plurality of signal buses are provided (notshown), with each column line being associated with each of the signalbuses via corresponding column selection switches, as explained abovewith respect to FIG. 3. Alternatively, it is, however, also possiblewith a plurality of signal buses for each column line to be associatedwith each of the signal buses, with the respective column line, however,not being associated with all of the output lines of the respectivesignal bus.

In FIGS. 1 to 4, the signals of the pixels P of the respective column ofthe respective column group S₁, S₂, . . . are applied in the form ofvoltage signals at the output amplifiers V₁, V₂, V₃, V₄ in ordersubsequently to be converted in each case by means of an A/D converter(not shown) into a respective digital value.

The pixels P of the image sensor are preferably active pixels in whichthe charge signals are already converted into voltage signals in thepixels P. The pixels P can, however, generally also be made as passivepixels in which the conversion of the charge signals into voltagesignals takes place on the signal path from the pixels P to the outputamplifiers A₁, A₂, A₃, A₄. The column selection switches 19 and the busselection switches 25 can, for example, be CMOS transistors.

The use of four output lines, four column lines per column group, fouroutput amplifiers or of two, three, four or five signal buses is only ofan exemplary nature. Any desired other number of output lines, columnlines per column group, output amplifiers or signal buses can generallybe provided.

1. An image sensor for electronic cameras, comprising a plurality oflight sensitive pixels (P) arranged in rows ( . . . , Z_(m-1), Z_(m))and columns (S₁₋₁, . . . , S₁₋₄, S₂₋₁, . . . , S₂₋₄, . . . ); a numberof output amplifiers (V₁, V₂, V₃, V₄); a switching device (11, 13), forselectively switching the pixels (P) of one of the rows ( . . . ,Z_(m-1), Z_(m)) to the number of output amplifiers (V₁, V₂, . . . , V₄);and a control device (17) for controlling the switching device (11, 13),characterized in that the image sensor is made such that an order inwhich the plurality of light sensitive pixels (P) are switched to theoutput amplifiers (V₁, V₂, V₃, V₄) is varied with respect to the orderin which the plurality of light sensitive pixels (P) are arranged alonga row ( . . . , Z_(m-1), Z_(m)) of the image sensor; wherein the columns(S₁₋₁, . . . , S₁₋₄, S₂₋₁, . . . , S₂₋₄, . . . ) are divided into aplurality of column groups (S₁, S₂, . . . ); and in that the number ofthe output amplifiers (V₁, V₂, V₃, V₄) corresponds to the number of thecolumns (S₁₋₁, . . . , S₁₋₄, S₂₋₁, . . . , S₂₋₄, . . . ) of a columngroup (S₁, S₂, . . . ), with the number of columns (S₁₋₁, . . . , S₁₋₄,S₂₋₁, . . . , S₂₋₄, . . . ) of each column group (S₁, S₂, . . . ) beingassociated with the number of output amplifiers (V₁, V₂, V₃, V₄) inaccordance with an association order, and with mutually differentassociation orders being provided for at least some of the plurality ofcolumn groups (S₁, S₂, . . . ).
 2. An image sensor in accordance withclaim 1, characterized in that all of the column groups (S₁, S₂, . . . )have the mutually different association orders.
 3. An image sensor inaccordance with claim 1, characterized in that the mutually differentassociation orders are provided for adjacent column groups (S₁, S₂, . .. ).
 4. An image sensor in accordance with claim 1, characterized inthat the image sensor has at least one signal bus (B₁, B₂, B₃) each ofwhich includes a number of output lines (A₁, A₂, A₃, A₄) whichcorresponds to the number of the output amplifiers (V₁, V₂, V₃, V₄),with the columns (S₁₋₁, . . . , S₁₋₄, S₂₋₁, . . . , S₂₋₄, . . . ) of arespective column group (S₁, S₂, . . . ) being connected or connectableto different ones of the output lines (A₁, A₂, A₃, A₄) of the at leastone signal bus (B₁, B₂, B₃) at predetermined association points (Z),with the association order being preset by the arrangement of thepredetermined association points.
 5. An image sensor in accordance withclaim 1, characterized in that the image sensor has a plurality ofsignal buses (B₁, B₂, B₃) which each includes a number of output lines(A₁, A₂, A₃, A₄) which corresponds to the number of output amplifiers(V₁, V₂, V₃, V₄), with the switching device (15) being made to switchthe output lines (A₁, A₂, A₃, A₄) of a respective one of the pluralityof signal buses (B₁, B₁, B₃) selectively to the output amplifiers (V₁,V₂, V₃, V₄).
 6. An image sensor in accordance with claim 5,characterized in that the control device (17) is made to control theswitching device (15) such that two column groups (S₁, S₂, . . . )switched sequentially to the output amplifiers (V₁, V₂, V₃, V₄) areswitched via different ones of the signal buses (B₁, B₂, B₃) to theoutput amplifiers (V₁, V₂, V₃, V₄).
 7. An image sensor in accordancewith claim 5, characterized in that at least some of the column groups(S₁, S₂, . . . ) are associated with a plurality of signal buses (B₁,B₂, B₃), with the association orders within each such column group (S₁,S₂, . . . ) being different for the plurality of signal buses (B₁, B₂,B₃).
 8. An image sensor in accordance with claim 5, characterized inthat the control device (17) is made to control the switching device(15) such that the signal buses (B₁, B₂, B₃) from row ( . . . , Z_(m-1),Z_(m)) to row ( . . . , Z_(m-1), Z_(m)) are switched to the outputamplifiers (V₁, V₂, V₃, V₄) in a different order.
 9. An image sensor inaccordance with claim 5, characterized in that the control device (17)is made to control the switching device (11, 13) such that, within arespective column group (S₁, S₂, . . . ), the columns (S₁₋₁, . . . ,S₁₋₄, S₂₋₁, . . . , S₂₋₄, . . . ) from row ( . . . , Z_(m-1), Z_(m)) torow ( . . . , Z_(m-1), Z_(m)) are switched to different signal buses(B₁, B₂, B₃).
 10. An image sensor in accordance with claim 5,characterized in that the control device (17) is made to completely readout the image sensor using a predetermined number of signal buses (B₁,B₂), with the image sensor having more signal buses (B₁, B₂, B₃) thanthe predetermined number of signal buses.
 11. An image sensor inaccordance with claim 1, characterized in that the columns (S₁₋₁, . . ., S₁₋₄, S₂₋₁, . . . , S₂₋₄, . . . ) are divided into a plurality ofcolumn groups (S₁, S₂, . . . ) and the number of the output amplifiers(V₁, V₂, V₃, V₄) corresponds to the number of columns (S₁₋₁, . . . ,S₁₋₄, S₂₋₁, . . . , S₂₋₄, . . . ) of a column group (S₁, S₂, . . . ),with the column groups (S₁, S₂, . . . ) being arranged in accordancewith an arrangement order relative to one another and the control device(17) being made to control the switching device (11, 13) such that thecolumn groups (S₁, S₂, . . . ) are switched for each row in accordancewith a respective readout order sequentially to the output amplifiers(V₁, V₂, V₃, V₄), with the respective readout order of the column groups(S₁, S₂, . . . ) being different from the arrangement order of thecolumn groups (S₁, S₂, . . . ).
 12. An image sensor for electroniccameras, comprising a plurality of light sensitive pixels (P) arrangedin rows ( . . . , Z_(m-1), Z_(m)) and columns (S₁₋₁, . . . , S₁₋₄, S₂₋₁,. . . , S₂₋₄, . . . ); a number of output amplifiers (V₁, V₂, V₃, V₄); aswitching device (11, 13), for selectively switching the pixels (P) ofone of the rows ( . . . , Z_(m-1), Z_(m)) to the number of outputamplifiers (V₁, V₂, . . . , V₄); and a control device (17) forcontrolling the switching device (11, 13), characterized in that theimage sensor is made such that an order in which the plurality of lightsensitive pixels (P) are switched to the output amplifiers (V₁, V₂, V₃,V₄) is varied with respect to the order in which the plurality of lightsensitive pixels (P) are arranged along a row ( . . . , Z_(m-1), Z_(m))of the image sensor; wherein the columns (S₁₋₁, . . . , S₁₋₄, S₂₋₁, . .. , S₂₋₄, . . . ) are divided into a plurality of column groups (S₁, S₂,. . . ) and the number of the output amplifiers (V₁, V₂, V₃, V₄)corresponds to the number of columns (S₁₋₁, . . . , S₁₋₄, S₂₋₁, . . . ,S₂₋₄, . . . ) of a column group (S₁, S₂, . . . ), with the column groups(S₁, S₂, . . . ) being arranged in accordance with an arrangement orderrelative to one another and the control device (17) being made tocontrol the switching device (11, 13) such that the column groups (S₁,S₂, . . . ) are switched for each row in accordance with a respectivereadout order sequentially to the output amplifiers (V₁, V₂, V₃, V₄),with the respective readout order of the column groups (S₁, S₂, . . . )being different from the arrangement order of the column groups (S₁, S₂,. . . ).
 13. An image sensor in accordance with claim 12, characterizedin that the control device (17) is made to control the switching device(11, 13) such that the readout order is varied for at least some of therows from row ( . . . , Zm−1, Zm) to other row ( . . . , Zm−1, Zm).